A device for enriching air with oxygen is known from DE 101 42 946 A1. The hot air which is entrained with water vapour is cooled in a heat exchanger and reaches a water separator with which the condensation product is removed. The product gas enriched with oxygen is produced by way of two, parallel arranged molecular sieve beds which function alternately in an adsorption operation and a desorption operation. For desorption of the molecular sieve bed which is not used, a part of the product gas is used as a rinsing gas flow which flows through the molecular sieve bed located in regeneration operation. A change-over valve which is connected in front of the molecular sieve beds switches between the adsorption and desorption phase.
The known device continuously supplies the produced product gas continuously into the consumer conduit. At the same time it often occurs that after the onset of operation the full output of the molecular sieve bed operating in the adsorption phase is not usually available. The full adsorption output is present if the molecular sieve beds have reached the stationary operating point. During the initial running phase the product gas flow therefore only has an oxygen component which lies below the threshold value required for operation.